Solve for $g$. $-0.4=\dfrac g3-0.9 $
Explanation: Let's add and then multiply to get $g$ by itself. $\begin{aligned} -0.4&=\dfrac g3-0.9 \\ \\ -0.4{+0.9} &=\dfrac g3-0.9 {+0.9}~~~~~~{\text{add }0.9} \text{ to each side}\\ \\ -0.4{+0.9}&=\dfrac g3-\cancel{ 0.9} {{+}\cancel{{0.9}}}\\ \\ -0.4{+0.9}&=\dfrac g3 \end{aligned}$ $\begin{aligned}0.5&= \dfrac g3 \\ \\ {0.5}\cdot{{3}} &= \dfrac g{3}\cdot{{3}} ~~~~~~~\text{multiply each side by } {3} \text{ to get } g \text{ by itself }\\ \\ {0.5}\cdot{{3}} &= \dfrac g{\cancel{3}}\cdot{\cancel{{3}}} \\ \\ {0.5}\cdot{{3}} &= g \end{aligned}$ The answer: $g={1.5}$ Let's check to make sure. $\begin{aligned} -0.4&=\dfrac g3-0.9 \\\\ -0.4&\stackrel{?}{=} \dfrac{{1.5}}3-0.9 \\\\ - 0.4&\stackrel{?}{=} 0.5-0.9 \\\\ -0.4&= -0.4 ~~~~~~~~~~\text{Yes!} \end{aligned}$